lovecoding
/
VIP24


			
				
					
						
						
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							<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    img{
      position: absolute;
    }
  </style>
</head>

<body>
  <!-- <img src="img/1.png" alt=""> -->
  <script>
    //获取屏幕的宽高
    var screenWidth = document.body.clientWidth || document.documentElement.clientWidth;
    var screenHeight = document.body.clientHeight || document.documentElement.clientHeight;
    //构造函数 写属性
    function leaf() {
      //图片宽度
      this.width = Math.random() * 100 + 100;
      //图片距离左边的距离
      this.xLeft = Math.random() * (screenWidth - this.width)
      //距离顶部
      this.xTop = 0
      //图片路径
      this.bg = 'img/' + Math.floor(Math.random() * 4 + 1) + '.png'
      /* 
        如何让随机数为1，2，3，4整数
        Math.random() 0-1随机小数
        Math.random() * 4  0-4随机小数
        Math.random() * 4 + 1    1-5之间的随机小数  不包括5

        Math.floor() 向下取整   跟四舍五入没关系  
        Math.floor(Math.random() * 4 + 1)   1，2，3，4
      */
    }
    // 原型下面写方法
    leaf.prototype.init = function(){
      //创建img标签
      var oImg = document.createElement('img')
      //引用路径
      oImg.src = this.bg
      oImg.style.width = this.width + 'px'
      oImg.style.left = this.xLeft + 'px'
      oImg.style.top = this.xTop + 'px'
      this.img = oImg
      document.body.appendChild(oImg)
    }
    //下落的方法
    leaf.prototype.fall = function(){
      //叶子起始延迟时间
      setTimeout(function(){
        this.timer = setInterval(function(){
          console.log(this)
          if(this.img.offsetTop < screenHeight - this.img.offsetHeight){
            this.img.style.top = this.img.offsetTop + 10 + 'px'
          } else {
            clearInterval(this.timer)
          }
        }.bind(this),20)
        // console.log(this)
      }.bind(this),Math.random()*2000)
      // console.log(this)
    }
    var leafArr = []
    for (var i = 0; i < 20; i++) {
      //创建实例化对象
      var leaf1 = new leaf()
      leafArr.push(leaf1)
      leaf1.init()
    }
    document.onclick = function(){
      for(var i=0;i<leafArr.length;i++){
        leafArr[i].fall()
      }
    }
  </script>
</body>

</html>